Cascaded spiral microfluidic device for deterministic and high purity continuous separation of circulating tumor cells

Inertial microfluidics is an emerging class of technologies developed to separate circulating tumor cells (CTCs). However, defining design parameters and flow conditions for optimal operation remains nondeterministic due to incomplete understanding of the mechanics, which has led to challenges in designing efficient systems. Here, we perform a parametric study of the inertial focusing effects observed in low aspect ratio curvilinear microchannels and utilize the results to demonstrate the isolation of CTCs with high purity. First, we systematically vary parameters including the channel height, width, and radius of curvature over a wide range of flow velocities to analyze its effect on size dependent differential focusing and migration behaviors of binary (10 μm and 20 μm) particles. Second, we use these results to identify optimal flow regimes to achieve maximum separation in various channel configurations and establish design guidelines to readily provide information for developing spiral channels tailored to potentially arbitrary flow conditions that yield a desired equilibrium position for optimal size based CTC separation. Finally, we describe a fully integrated, sheath-less cascaded spiral microfluidic device to continuously isolate CTCs. Human breast cancer epithelial cells were successfully extracted from leukocytes, achieving 86.76% recovery, 97.91% depletion rate, and sustaining high viability upon collection to demonstrate the versatility of the device. Importantly, this device was designed without the cumbersome trail-and-error optimization process that has hindered the development of designing such inertial microfluidic systems.     

A comparison of methods of observation in preservice teacher training

Summary This study tested the hypothesis that different techniques of classroom observation result in different degrees of learning by teachers-in-training. Specifically, it was predicted that kinescope recordings (prepared in advance) provide a more effective medium of observation than closed-circuit television and that TV observation is in turn more effective than the traditional procedure of direct observation in the classroom. The logical theoretical basis for this hypothesis and the special conditions of experimentation used in this study were elaborated. Measures of two dependent variables were used to test this hypothesis. One measure of the students’ response to these observational techniques, an objective multiple-choice measure of information about methods of teaching, failed to confirm the hypothesis, but did show systematic variation with several other experimental variables. The other measure, an essay examination assessing ability to evaluate an observed classroom lesson critically, revealed strong confirmation of the hypothesis. Several other results emerged. One significant finding indicated that when used by certain instructors, the differential effect of the observational condition can outweigh the very great importance of general scholastic ability as a correlate of gain in learning. Interpretations of these data were made to clarify the role of classroom observation in the teacher training process. This research was supported by a grant from the Educational Media Branch of the U.S. Office of Education.     

‘Basic Values’ and Education

The Personal Adviser is a new role within schools. It is an integral part of the new Connexions Service, which is being implemented throughout England in tranches, the first starting in April 2001. This article examines the origins of the role, the confusion that has surrounded its initial development, and some of the issues that it will have to confront. The paper draws on experience gained in some of the Connexions pilot schemes during 2000/1.     

Image and Experience of Contemporary Public Schools: informal processes and the post‐school transition

This paper considers the role of informal networks in securing post‐public school occupational advantage. Both the ‘official’ view of the private sector and the experiences of recent pupils are cited. A significant disparity is found between the two. A denial of the relevance of the ‘old boy network’ is revealed in the sector's publications, a position fully consistent with the overall reconstruction of image currently being pursued. In contrast, ex‐pupils unequivocally asserted the continued influence of non‐meritocratic means of advancement, though crucially, only for an (elite) element of pupils. It is argued that adequate social analysis requires not simply an awareness of the presence of covert mechanisms, but also an acceptance of the socially restricted, rather than universally available, nature of the processes. Recognition is needed that contemporary informal networks have evolved from an historically familiar form, yet constitute a particular, dynamic, era‐specific manifestation of it.